Traditionally, when telephone calls or mails are exchanged by using mobile information devices such as portable telephone, normally such telephone or mail information is stored by means of a durable storage unit mounted inside the device (hereinafter referred to as “internal storage”), and it is generally and widely managed by the user. Such a device enables the user to call up the information when the user needs it and use it, and provides convenience to the user.
For example, a portable telephone includes a telephone directory function, which can be used to register in advance telephone number and mail address information in the internal memory, and to select an item in the directory to send a call. And the information of calls or mails received by a portable telephone and that of calls or mails sent by the user from a portable telephone is generally stored in the internal memory of the portable telephone as historical information, and such information can be used in other occasions to retransmit the call or mail.
Thus, the possibility of storing information of telephone calls or mails in the storage of the portable telephone or mobile information system is desirable in that it provides convenience of providing the user with a convenient method of communication. However, on the other hand, saving in such an internal storage creates another problem, i.e. the problem of security.
For example, when a portable telephone is lost, the information saved in the internal storage of the portable telephone is stolen by a person other than the user of the portable telephone by using all the possible means (information leaks). Therefore, there is a problem in that such portable telephone or mobile information device cannot provide a high information security.
In view of such a problem, as shown below, means such as the one described in JP-A No. 2003-078624, “Hitachi Ltd., Security PC, Flora Series Catalogue, CA-499Y, issued in June 2007” was provided in the past.
JP-A No. 2003-078624 discloses a system enabling a customer and a store to talk without allowing the store to learn the telephone number of the customer by letting the customer and the store talk through a reservation and call management system. The use of such a system eliminates the possibility of the customers making direct calls to the store, and therefore the store receives no direct telephone calls from the customers, and there will be no problem of leakage of customer information from the store system. And the telephone number of the store does not remain (is not stored) in the customer's portable telephone, and only the telephone number of the reservation call system remains in its place. And therefore, the leakage of telephone number of the store from the customer's portable telephone is avoided.
“Hitachi Ltd., Security PC, Flora Se Series Catalogue CA-499Y, issued in June, 2007” describes a computer called Security PC. In such a device, independently from the Security PC operated by the user, a computer called “server” and disposed in a remote environment exists being connected with the network. In the security PC, no hard disk drive is mounted on the terminal operated by the user. In its place, all the information is stored in the server, and the information required by the security PC is obtained from the server through a network. In this way, the security PC enables to prevent the leakage of information by not storing any information in a durable memory.